package com.test.newJdk8;

import java.util.Optional;

/**
 * @ Author xsd
 * @ crate time 2020/10/19 11:50
 * @ 描述
 */
public class Java8Tester {
    /**
     * 空-null.
     * Optional<Integer> a = Optional.ofNullable(value1);
     * Integer value1 = a.orElse(new Integer(0));
     * 非空.
     * Optional<Integer> b = Optional.of(value2);
     * Integer value2 = b.get();
     *      b.isPresent()
     *
     *  String serNo = (String)Optional.ofNullable(body.getStr("serNo")).orElse("");
     */
    public static void main(String args[]) {
        Java8Tester java8Tester = new Java8Tester();
        Integer value1 = null;
        Integer value2 = new Integer(10);

        // Optional.ofNullable - 允许传递为 null 参数
        Optional<Integer> a = Optional.ofNullable(value1);
        // Optional.of - 如果传递的参数是 null，抛出异常 NullPointerException
        Optional<Integer> b = Optional.of(value2);
        System.out.println(java8Tester.sum(a, b));
    }

    public Integer sum(Optional<Integer> a, Optional<Integer> b) {
        // Optional.isPresent - 判断值是否存在
        System.out.println("第一个参数值存在: " + a.isPresent());
        System.out.println("第二个参数值存在: " + b.isPresent());
//        System.out.println(a.get()); // java.util.NoSuchElementException: No value present
        // Optional.orElse - 如果值存在，返回它，否则返回默认值
        Integer value1 = a.orElse(new Integer(0));
        //Optional.get - 获取值，值需要存在
        Integer value2 = b.get();
        return value1 + value2;
    }
}
